This invention relates to improved inertia actuated shock responsive devices for automatically operating a controlled unit upon subjection of the device to shock forces of predetermined intensity, such as for example the forces encountered in an earthquake, explosion, or the like. The invention will be described primarily as utilized for operating a valve as the controlled unit, typically for the purpose of closing off the delivery of gas in a pipe line in the event of an earthquake, but may also be applied to actuation of other types of controlled units, such as an electric switch.
Certain types of shock responsive actuators have been provided in the past, including for example the device disclosed in U.S. Pat. No. 4,185,507 issued Jan. 29, 1980 to Frank F. Domyan. These prior devices have in common the fact that they include an inertia actuated weight mounted in association with a coacting structure which moves relative to the weight upon subjection to seismic or other shock forces, with the weight resisting displacement with the structure by virtue of its inertia. The relative movement between that structure and the weight is then utilized to effect actuation of the controlled valve or other unit. In the apparatus of the above identified patent and in other prior arrangements, the weight and other moving parts of the device are contained within a housing which forms a portion of the structure movable relative to the weight, with the housing being sealed and its interior being in communication with the gas pipe line.